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By Authority Of 


Legally Binding Document 

By the Authority Vested By Part 5 of the United States Code § 552(a) and 
Part 1 of the Code of Regulations § 51 the attached document has been duly 
INCORPORATED BY REFERENCE and shall be considered legally 
binding upon all citizens and residents of the United States of America. 
HEED THIS NOTICE : Criminal penalties may apply for noncompliance. 

Document Name: SAE J1292: Automobile, Truck, Track-Tractor, Trailer, 

and Motor Coach Wiring 

CFR Section(s): 49 CFR 393.28 

Standards Body: Society of Automotive Engineers 



SAE Recommended Practice 

Report of the SAE Electrical Equipment Committee approved June 1980, editoral change October 1981. 

[This SAE Recommended Practice combines, revises, and replaces two previ- 
ous recommended practices: SAE J555a and SAE J556.] 

Foreword—This Document has not changed other than to put it into the new 
SAE Technical Standards Board Format. 

h Scope— This SAE Recommended Practice covers the application of primary 
wiring distribution system harnesses to automotive, truck, and similar type vehi- 
cles. This is written principally for new vehicles but is also applicable to rewiring 
and service. It covers the areas of performance, operating integrity, efficiency, 
economy, uniformity, facility of manufacturing and service. This practice applies 
to wiring systems of less than 50 V. 

2. References 

2.1 Applicable Publications— The following publications form a part of 
this specification to the extent specified herein. Unless otherwise indicated, the 
latest version of SAE publications shall apply. 

2.1.1 SAE Publications— Available from SAE, 400 Commonwealth Drive, 
Warrendale, PA 15096-0001. 

SAE J156— Fusible Links 

SAE J163— Low Tension Wiring and Cable Terminals and Splice Clips 

SAE J25 8— Circuit Breaker— Internal Mounted— Automatic Reset 

SAE J541— Voltage Drop for Starting Motor Circuits 

SAE J553— Circuit Breakers 

SAEJ554 — Electric Fuses (Cartridge Type) 

SAE J560— Seven Conductor Electrical Connector for Truck-Trailer Jumper 

SAE J561— Electrical Terminals— Eyelet and Spade Type 

SAE J573— Miniature Lamp Bulbs 

SAE J575— Test Methods and Equipment for Lighting Devices and Compo- 
nents for Use on Vehicles Less Than 2032 mm in Overall Width 

SAE J858— Electrical Terminals— Blade Type 

SAE J895— Five Conductor Electrical Connectors for Automotive Type Trail- 

SAE J928 — Electrical Terminals — Pin and Receptacle Type 

SAE J1067— Seven Conductor Jacketed Cable for Truck Trailer Connections 

SAE Jl 127— Battery Cable 

SAE Jl 128— Low-Tension Primary Cable 

2.1.2 ASTM Publication— Available from ASTM, 100 Barr Harbor Drive, 
West Conshohocken, PA 19428-2959. 

ASTM D 573— Test Method for Rubber — Deterioration in an Air Oven 
_ 3. General Section 

3.1 Definition — The- systems of installation known as two wire or single 
wire are to be designated respectively as insulated-return and ground-return sys- 
tems. Installations in which the frame and/or body of the vehicle are used as part 
of the return circuit are considered as ground-return systems. 

3.2 Insulated Cable— All insulated cable shall conform to SAE Standards 

3.2.1 Conductors 

3.2. 1.1 . All conductors are to be constructed in accordance with SAE Jl 127 
and J1128 except when good engineering practice dictates special strand con- 
structions. Conductor materials and stranding other than copper can be used if 
all applicable requirements for physical, electrical, and environmental conditions 
are met as dictated by the end application. . 

3.2.2 Conductor Insulation— Physical and dimensional values of conduc- 
tor insulation are to be in conformance with the requirements of SAE J1127 or 
J1128 except when good engineering practice dictates special conductor insula- 

3.3 Insulated Cable Application 

3.3.1 Select cable insulation in accordance with the vehicle's working environ- 
ment. Consideration is given to physical and environmental factors such as flex- 
ing, heat, cold, bend, oil and fuel contact, dielectric, abrasion, short circuit, and 
pinch resistance among others. 

Note: Most vehicle working environments permit the use of a thermoplastic 
insulated, SAE type GPT, general purpose cable. A cable of this type is generally 

used in static (non-flexing) applications when nominal abrasion, heat, cold, oil, 
dielectric, short circuit, and pinch resistance properties are desired. 

3.3.2 Where vehicle working environments for cable require additional physi- 
cal and environmental characteristics, upgraded insulations such as SAE types 
HDT, GPB, HDB, STS, HTS, and SXL shall be used as the severity of the appli- 
cations dictate. 

3.3.3 Specific continuous duty temperature limitations for each SAE cable type. 
shall be observed. The total of the ambient temperature plus cable temperature 
rise, due to current flow, should not exceed the continuous duty guideline temper- 
atures as shown in Table 1, unless extensive testing and/or evaluation has indi- 
cated that higher temperatures can be tolerated. 

In addition, the maximum continuous duty temperature rating for any wire 
insulation shall be determined by an accelerated aging test conducted in accor- 
dance with ASTM D 573, with the samples of insulation being removed from the 
finished wire and aged 168 h. The test temperature shall be 30 °C above the 
intended rated temperature. . Tensile strength after aging shall be not less than 
80% of the original tensile strength. The elongation after aging shall be at least: 
50% of the original elongation. 

Note: Heavier conductors may be required to protect the carrying of current in 
wire bundles when all conductors are carrying maximum current. Temperature 
rise tests of the conductor bundle shall be run to determine the proper conductor 
size and insulation. 

Resistance wire low tension cable may be used to limit the voltage applied to 
electrical devices. Since the nature of the wire is to limit the voltage applied to 
electrical devices, the distance of the device from the power source and the cur- 
rent demand of the device will determine the materials used. Because every. 
application is different, no materials, conducting or insulating, can be specifically 
described as standard; thus the conductor and insulating materials must be care- 
fully chosen for each application by the design engineer. It is desirable to identify, 
resistance wire by printing the words resistance wire on the conductor. 

Extreme care shall be used by the design engineer in choosing resistance wire 
as a conducting material to satisfy the current demand of the device and not create 
a temperature rise in the conductor that would deteriorate the insulating material 
even though the device is left on continuously. 

Circuits using resistance wire shall be carefully placed in the vehicle so that 
their temperature rise will not create a hazard to, or malfunction of, any part of the 
vehicle. A general design guide would be that the conductor will be required to 
dissipate no more than 5 W per insulated conductor foot. 


SAE Cable (Ref. SAE J1128) 

Type STS, HTS 
.Type SXL .. -. - 

Temperature^ 1 ) 


1 . Recommended maximum continuous duty temperature {ambient plus rise). - 

3.3.4 FUSIBLE LINKS — A special section of low tension cable designed to open 
circuit when subjected to an extreme current overload shall conform to SAE 1156. 

3.3.5 It is desirable to color code each conductor in an electrical circuit to facil- 
itate manufacture and service of a wire assembly. It is further desirable for all 
motor vehicle manufacturers to assign and use similar color code information for 
commonly used electrical circuits to promote ease of circuit analysis in service 
among the various manufacturers. When feasible each circuit shall conform to a recommended color 
code by category of equipment as shown in Table 2. Otherwise, the color code 
may be a solid color (basic) and/or a basic color with secondary color stripes, 
dots, or hashes. : . , .--■ 

NOTE — The above code is identical to the color code adopted for- automo- 
tive type trailers - SAE J895. Secondary color markings to be applied as to be visible throughout 
the entire length of the wire, or at each end of a lead. 



Function v ~. 

Color .. 

Left rear stop and turn 

Yellow ..-..■ -.— -:.- 

Right rear stop and turn 

Dark green 



Tail, side marker, license ' 


Ground -■.-■■: 

White ■! " 

3^3:5.3 Color combinations for special circuits riot shown on Table 2 are to 
be selected by the user; As special circuit ftinctioris-becbrae^standard with manu- 
facturers, they shall be added to the recommended Color Code by category and 
shown in Table 2. • ' v^ ■-, ..-?■ 

NOTE— It is desirable for the wire Of any one circuit to be of uniform color 
: ; code .throughout the circuit regardless of the number of corinec- 
; tions; A circuit is'assumed to be continuous until it can be inter- 

rupted by a relay or switch contacts, or when it reaches a load (such 
as bulbs; riiotbrs^ etc.). Fusible links may differ in ; color from the 
1 circuits they are protecting as it could be advantageous to identify 
1 ■" fusible link wire gauge size by insulation color. 

'"■ Eaeh'eircUit irithe same wire assembly shall be distinguished from 
orieanotherin some marmer such as color code, or some substantial difference in 
insulation diameter (that is; two of iriore gauge sizes). r 
3.4 Conductor Termination 
3.44 All stranded conductor stripped ends are to be fitted with terminals 
(exception-splices); Solidj precisely shaped conductors whose ends are the termi- 
nation shall not Have this fitting. - 

3.4.2 All terminal attachments to conductors shall conform with the physical 
arid electrical-performance requirements bfSAEJ163. 

3.4.3 lAs a general practice; all terminations have integral and functional insu- 
lation grips, except where other secondary applications preclude their use. Spe- 
cial applications without irisulation grips may be employed where other means of 
retieving-strairi are provided;- 

3.4.4 ! A terminal shall be attached to a Conductor by a simple mechanical 
crimp-type process that will cbrafonri to the intent of paragraph 3.4.2/ For'maxi 1 
mum reliability and surety of connection, the crmip riiay als6 be soldered, 
swagged; brazed* or welded in a ^workmanlike manner: Care shall be taken to 
riiiriimize wicking'of solder ma stranded wire to avoid impairment of the strain 
relief oi: cable flexing. ; -■■'■' 

3.4.5 Circuit Grounding — Ground terminal lugs shall be solder dipped, cad- 
mium, tin, or zinc plated. Ground terminals shall be accessible for service: A ser- 
rated paint cutting terminal may be utilized to make proper contact on painted 
surfaces. Ground terminal devices shall be eadmium,-.tin^ or zinc plated. In spe- 
cial cases, plating may not be required for lugs and/or attaching devices. 

Ground return connections shall be made to the vehicle structure, frame, or 
engine. In cases where the engine or body is mounted on rubber or other insula- 
tion, proper ground shall be provided. 

3.4.5 Terrioinatibris used shall comply with the requirements of SAE J561, ring 
and spade. types; ;S%E J858,.blade type;..and SAEJ928, pin and receptacle type. 
Secondary applications will dictate the use of special terminations for special use 
or application. 

NOTE-^Termmatibns may be .plated with a conductive and corrosion resistant 
material such as tin or silver to upgrade the current carrying capacity 
and to improve their resistance to corrosion. 

3.5 Conductor, Splicing " : r t^ ? ; 

3.5.1 Conductors shall be mechanically crimped, soldered, swagged, brazed, or 
welded with other conductors to form a, wire splice., All wire splices shall con- 
form with the electrical specifications fdr T spiices per SAE J163. ; ' ; ° •'"'"' 

3:5.2 "Splices' shall be mechanically secure to withstand all fabrication installa- 
tion and vehicle environment abuse. The splice must be insulated. 

3.6 Terminal and Connector Function 

3.6.1 -Single terminations shall be used only where there is no possibility of 
misconnections in assembly or service except when special applications may 
require otherwise. 

3.6.2 Multiple terminal connect-disconnect connector bodies shall be used at 
all points where two or more conductors are terminated and 1 where there isa pos- 
sibility of misconriection in fabrication^ assembly, or service; secondary applica- 
tions may require a deviation from this practice. '■'-■- 

3.6.3 All connections shall be- designed to maintain surety of connections 
while subjected to vibration, shock, arid the extreme temperatures that are normal 
environmental conditions for motor vehicles. "Surety may be accomplished by 
employing the use of integral-molded lock devices, terminal to teramial interfer- 
ences (detents), secondary locking clips, or attaching devices. r ' 

3.6.4 All multiple connect-disconnect connector bodies shall 1 be polarized to 
prevent incorrect assembly unless circuitry permits use of a nonpolarized connec- 
tor. : 

3.6.5 Connections shall be located in clean, dry areas when possible. Connec- 
tions shall be designed to maintain circuit integrity regardless of environmental 
conditions (such as high humidity, road splash, rain, drainage, earth particles, 
fuels, lubricants, high and low temperatures, and solvent). r - ; 

3.7 Conductor Grouping ■ 

3.7.1 Conductors are to be grouped together into multiple conductor assem- 
blies whenever possible. ..'-.■.■ 

3.7.2 The number of wiring assemblies arid electrical connections per vehicle 
shall be kept to a minimum with overlay or option wiring used only when justified 
by the economics of fabrication, vehicle installation, and service. 

3.8 Wire Assembly Construction 

3.8.1 Conductors are to be grouped, where practical^in cable or harness form. 
NOTE — Suitable material such as braided cotton, braided paper and cotton, 

braided vinyl/nylon, flexible plastic conduit, friction or thermoplastic 
tape; extruded rubber and thermoplastic jackets, or woven loom may 
be used to form the assembly. 

3.8.2 Wiring harness covering shall be adequate to protect the harness in the 
vehicle routing environment and shall furnish protection during all phase's of Vehi- 
cle assembly and operation. ■ [ ' -'* 

NOTE — A general guideline to be used in the selection of coverings' is speci- 
fied in Table 3. 

3.9 Wire Assembly Installation and Protection .'"''..'' 

3.9.1 Wiring and related devices shall be installed in a workmanlike mariner, 
mechanically and electrically secure. Devices, lamps, and so forth requiring ; peri- 
odic service shall be serviceable arid accessible by providing' wife length suffi- 
cient to reasonably accomplish this. -'' T : ' 

3.9.2 In general, wire routing shall be such that maximum protection is pro- 
vided by the vehicle sheet metal arid structural components. Smooth /protective 
channels especially designed for wiring and built into the veliicl& bbdy structure 
should be used when practicable. Avoid areas of excessive heat, vibration, arid 

NOTE — Extra protection (such as braid, loom, conduit, etc.) should be pro- 
vided when these areas cannot be avoided (Ref. Table. 3). 



Wire Harness Covering 

General Application - 

1 * Vinyl Plastic Tape - 01007 in (0.1 8mm) " Primarily used for grouping cables into wire harnesses. Wiring not subject to damage from 

scuffing or scrubbingon rough metal-edges. 

2 Friction Tape, Cotton and Kraft Paper Braid Generally optional; improved scuff and scrub resistance. 

3 Vinyl/Nylon Braid Improved abrasion resistance. 

4 '- Non-Metallic Loom (Woven Asphalt, Impregnated Loom, Extruded Vinyl Improved scuff and abrasion resistance. 

- Plastic, or Elastomeric Tubing) r 

5 Rigid and Flexible Conduit For maximum abrasion resistance and/or positive positioning for clearance to moving or heated 

i vehicle components. 

3.9.3 All parts of the electrical system shall be adequately protected against 

3.9.4 If significant vibration levels exist, the edges of all metal members 
through which cables and harnesses pass shall be deburred, flanged, rolled, or 
bushed with suitable grommets. Suitable tubing or conduit over cables may be 
substituted for grommets if properly secured. Clips for retaining cables and har- 
nesses shall be securely attached to body or frame member and cable or harness. 
Clips also assist in locating and routing at assembly. 

3.9.5 Wiring shall be located to afford protection from road splash, stones, 
abrasion, grease, oil, and fuel. Wiring exposed to such conditions shall be further 
protected by either, or a combination of, the use of heavy wall thermoplastic insu- 
lated cable, (see SAE Standard J1128, Low Tension Primary Cable) additional 
tape application, plastic sleeving or conduit, nonmetallic loom, or metallic or 
other suitable shielding or covering. 

3.9.6 Where cables must flex between moving parts, the last supporting clip 
shall be securely mounted and secure the cable in a permanent manner. 

3.9.7 Wiring fasteners shall be non-conductive unless the wiring or fastener 
involved is provided with extra heavy outer covering such as nonmetallic conduit, 
tape, or dip. 

NOTE— Overlay or option wiring should be routed in the same fasteners with 
standard wiring where practical, or should be fastened to the standard 
wiring with plastic straps or other mechanical means. 

3.9.8 Electrical apparatus with integral wiring shall be supplied with grommets 
or other suitable mechanical fasteners for strain relief. 

3.10 Wiring Overload Protective Devices 

3.10.1 The current to all low-tension circuits, except starting motor and igni- 
tion circuits, shall pass through short circuit protective devices connected to the 
battery feed side of switches. Headlight systems shall be independently pro- 
tected. Circuit protection shall be accomplished by utilizing fuses, circuit break- 
ers, or fusible links which conform to SAE Standards. 

3.10.2 The protective device shall be selected to prevent wire damage when 
subjected to extreme current overload. Fwsej— Fuse sizes shall be selected using guidelines presented in 
SAE J554, Electric Fuses. Circuit Breakers— Fail-safe automatic reset circuit breakers shall 
be employed when it is necessary to quickly re-establish circuit continuity when 
that portion of the wiring has been subjected to an overload condition. Non- 
cycling type circuit breakers will not reset until the overload is removed, (unless 
they are the non-cycling manual-reset type). Circuit breakers shall conform to 
SAEJ553andSAEJ258. Fusible links shall be employed when heavy feed circuits exceed 
the continuous working limits of the fuses or circuit breakers. The link of wire, 
acting like a fuse, shall conform to the guidelines presented in SAE J156, Fusible 

4. Truck, Truck-tractor Section 

4.1 The following SAE Recommended Practice relates to wiring for exte- 
rior lamps, exclusive of head lamps, of commercial vehicles 80 in (203 cm) or 
more in width. Except as noted, the wiring system shall conform to the guidelines 
of Section 3. 

4.1.1 Lamp— A lamp is a complete lighting unit. All lamps shall meet the 
requirements of SAE Standard J575, Lighting Equipment for Motor Vehicles. 
Lamps with pigtails not in excess of 12 in (30 cm) long shall have a minimum of 
16-gauge wire; pigtails in excess of 12 in (30 cm) long shall have wire gauge con- 
forming to the wiring requirements of the vehicle. 

4.1.2 Wire Size— To minimize voltage drops, the feed wire size for all circuits 
shall be a minimum of 12-gauge; branches or taps not in excess of 50 ft (15.2 m) 
in length shall be 14-gauge. The ground wire for insulated-return systems shall 
be equal to the respective feed wire. The main ground wire shall be a minimum of 

NOTE — In many cases 4 or 6 gauge may be required. 

4.1.3 Design Voltage OF Lamps— Reference SAE Standard J573, Lamp 
Bulb and Sealed Units for design voltage values applicable to various bulbs. 

4.1.4 Truck-tractors shall conform to Section 3 and the following: Circuit Identification—It is desirable to follow the SAE Recom- 
mended Practice J1067, Seven Conductor Jacketed Cable for Truck and Trailer 
Connections, for coding of truck-tractor jumper cable throughout the circuit. 
Where impractical, the coding is to be followed to a junction block or harness ter- 
minating point where visual inspection will identify the circuit coding change. 
The coding may also be numbers and/or letters printed on the wire insulation. 
Whatever coding system is chosen, the system shall facilitate in harness manufac- 
turing and in service. 


v Circuit Termination— Wiring for trailer circuits shall terminate in: 

a. A connector socket conforming to SAE Recommended Practice J560, 
Seven-Conductor Electrical Connector for Truck-Trailer Jumper Cable, 

b. A jumper cable with cable plug conforming to SAE J560. 

5. Trailer Section 

5.1 Trailers shall conform to Section 3 and the following: 

5.1.1 WIRING — All wiring shall be installed in: 

a. Suitable conduit and boxes, 

b. Structure of the trailer, and 

c. Housings and/or raceways which provide equal protection. 

Wiring shall be protected from stones, excess dirt, ice, moisture, chafing, and so 
forth, that will result in harmful effects. 

All wiring for legally required lights shall be serviceable in a manner permitting 
removal and reinstallation from outside the trailer. 

5.1.2 Grounding— The trailer shall be grounded to the tractor through the 
jumper cable. 

NOTE— Contact of the trailer king pin or apron plate with the lower coupler or 
grounding through the coupler is not to be considered as providing a 
tractor-to-trailer ground. 

5.1.3 Marking— The voltage of the lighting system shall be permanently or 
semi-permanently marked in a legible manner on a mounting surface, in proxim- 
ity to the electrical connector receptacle. Preferably, the marking shall be in 
amber reflective letters. 

5.1.4 Trailer Connector Socket— The trailer connector socket for receiv- 
ing the jumper cable plug shall conform to SAE J560. 

5.1.5 Circuit Protection— Circuit protection independent of truck-tractor 
system shall be provided. Trailer circuit protective devices shall conform to SAE 
Standard J554, Electric Fuses or SAE Recommended Practice J553, Circuit 
Breakers and shall be located near the trailer wiring connector socket and be 
readily accessible for service. 

6. Motor Coach Section 

6.1 Motor coaches shall conform to Section 3 and the following: 
6.1.1 Wiring — Where practical, wiring is to be located within the structure of 

the coach where it will not be subjected to damage by road splash, stones, grease, 

oil, fuel, or abrasion. 
Wiring so located that it will be subjected to more than normal wear or hard 

usage shall be equipped with a means of disconnecting from the main harness and 

be easily removable for replacement or repair. 
Wiring connections to lights mounted on the coach body shall be accessible 

from outside, with the light removed or through an access door in an interior trim 


7. Storage Battery Cables 

7.1 Definition— Battery cables provide the link between the battery(s) and 
the balance of the starting/charging circuit. Items that dictate the design are: 

7.1.1 Routing— Routing shall be established with the following guidelines: Areas of excessive heat, abrasion, and vibration are to be avoided. 
Extra protection (such as loom, conduit, tubing, heat shield, etc.) shall be pro- 
vided when these areas cannot be avoided. Grommets or ferrules and nipples shall be provided when routed 
through holes in the frame or sheet metal. Support at intervals of approximately 24 in (61 cm). Insulated or 
nonconductive supports shall be used. Provide strain relief for the battery and starter motor terminals as 
close to terminals as practical. Tailor such that the cables are not too loose nor too tight, consider- 
ing engine rocking due to torque changes. 

7.1.2 Voltage Drop — Voltage drop for starting motor circuits as recom- 
mended in SAE J541, determines the maximum drop allowed for the total crank- 
ing circuits from the battery to the starter motor and the return to the battery. 

7.1.3 Cable Size — Cable size is determined by knowing the system parame- 
ters and subtracting their fixed resistances (such as connections, starter solenoid, 
ground path other than the battery cable, etc.) from the total specified in para- 
graph 7.1.2. This remaining resistance is the maximum allowed for the battery 

7.1.4 Cable Construction— Cable construction is determined from the 
environment in which the battery cables must survive. Core Stranding— Cove stranding of conventional cable can be either 
bunched, concentric stranded, or rope lay. Bunched or concentric will suffice in 
most applications, except those requiring higher flex life. For larger cable sizes, 
rope stranding is needed for routing purposes as well. Battery strap is available 


for extreme iflex requirements and restricted space or routing problems. Refer- 1.1.4,3. Te7?mna/$— Terminals provide the connection to the battery, starter 

enceSAE;J1127. ■ / -: ^ solenoid, junction blocks, switches, and grounding locations. A multitude of dif- 

7.1:4:2 Insulation— Insulation provides electrical as well as environmental ferent types and styles are available for the variety of cable sizes. Also available 

protection for the core. Polyvinyl chloride (PVC) can be used in most applica- are sleeves and covers which provide additional circuit and corrosion protection, 

tions; cross-linked polyethylene, hypalonj neoprene; etc., 1 may be, needed for Reference SAEJ561 and SAEJ163. 
added protection against short circuit, high temperature, abrasion, etc. Reference 
SAE Jl 127 and Table 1. v